Lignocellulosic
biomass is the most abundant organic carbon source
and has received a great deal of interest as renewable and sustainable
feedstock for the production of potential biofuels and value-added
chemicals with a wide range of designed catalytic systems. However,
those natural polymeric materials are composed of short-chain monomers
(typically C6 and C5 sugars) and complex lignin
molecules containing plenty of oxygen, resulting in products during
the downstream processing having low-grade fuel properties or limited
applications in organic syntheses. Accordingly, approaches to increase
the carbon-chain length or carbon atom number have been developed
as crucial catalytic routes for upgrading biomass into energy-intensive
fuels and chemicals. The primary focus of this review is to systematically
describe the recent examples on the selective synthesis of long-chain
oxygenates via different C–C coupling catalytic processes,
such as Aldol condensation, hydroalkylation/alkylation, oligomerization,
ketonization, Diels–Alder, Guerbet, and acylation reactions.
Other integrated reaction steps including, for example, hydrolysis,
dehydration, oxidation, partial hydrogenation, and hydrodeoxygenation
(HDO) to derive corresponding key intermediates or final products
are also reviewed. The effects of catalyst structure/type and reaction
parameters on the catalytic performance along with relevant reaction
mechanisms are in detail discussed. Apart from this, the formation
of other useful compounds containing C–X bonds (X = O, N, and
S) derived from biomass-based substrates for producing fuel additives
and valuable chemicals is also briefly reviewed.
BackgroundHylocereus polyrhizus and Hylocereus undatus are two varieties of the commonly called pitaya fruits, and pitaya fruits have gained popularity in many countries all over the world. However, studies on chemical composition and the nutritional quality of pitaya flesh peel are limited.ResultsExtracts of pitaya (H. polyrhizus and H. undatus) peel were extracted by supercritical carbon dioxide extraction, and analyzed by gas chromatography–mass spectrometry analysis. Their cytotoxic and antioxidant activities were investigated. The main components of H. polyrhizus extract were β-amyrin (15.87%), α-amyrin (13.90%), octacosane (12.2%), γ-sitosterol (9.35%), octadecane (6.27%), 1-tetracosanol (5.19%), stigmast-4-en-3-one (4.65%), and campesterol (4.16%), whereas H. undatus were β-amyrin (23.39%), γ-sitosterol (19.32%), and octadecane (9.25%), heptacosane (5.52%), campesterol (5.27%), nonacosane (5.02%), and trichloroacetic acid, hexadecyl ester (5.21%). Both of the two extracts possessed good cytotoxic activities against PC3, Bcap-37, and MGC-803 cells (IC50 values ranging from 0.61 to 0.73 mg/mL), and the activities of their main components were also studied. Furthermore, these extracts also presented some radical scavenging activities, with IC50 values of 0.83 and 0.91 mg/mL, respectively.ConclusionThis paper provides evidence for studying the chemical composition of supercritical carbon dioxide extracts of pitaya peel and their biological activity.
2-Cyanoacrylate is an important kind of herbicide targeted in photosystem II. Starting from cyano ethyl acetate, the chiral title compounds were synthesized under microwave irradiation, which has the advantages of shorter reaction time, higher yield, and simpler procedure. A half-leaf method was used to determine the inhibition and curative efficacies of the eight chiral products against tobacco mosaic virus in vivo. It was found that chiral compound IIc-R possesses moderate inhibition and curative effect in vivo with rates of 89.1 and 43.1%, respectively. In the MTT test, these new chiral compounds were found to possess weak antiproliferation activities to PC3 and A431 cells.
Catalytic transfer hydrogenation (CTH) reactions are efficient transformation routes to upgrade biobased chemicals. Herein, we report a facile and template-free route to synthesize a series of heterogeneous nitrogen-containing alkyltriphosphonate− metal hybrids with enhancive Lewis acid and base sites, and their catalytic activity in converting biomass-derived carbonyl compounds to corresponding alcohols in 2-propanol. Particularly, a quantitative yield of furfuryl alcohol (FFA) was obtained from furfural (FUR) over organotriphosphate−zirconium hybrid (ZrPN) under mild conditions. The presence of Lewis basic sites adjacent to acid sites with an appropriate base/acid site ratio (1:0.7) in ZrPN significantly improved the yield of FFA. Mechanistic studies for the transformation of FUR to FFA with ZrPN in 2-propanol-d 8 evidently indicate CTH reaction proceeding via a direct intermolecular hydrogen transfer route. It was also found that ZrPN could catalyze isomerization of C 3 −C 6 aldoses to ketoses involving intramolecular hydrogen transfer in water.
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